bpo-30459: Cast the result of PyList_SET_ITEM() to void (GH-19975)

Do the same for PyTuple_SET_ITEM().

Author: ZackerySpytz

Include/cpython/listobject.h

@@ -30,5 +30,5 @@ PyAPI_FUNC(void) _PyList_DebugMallocStats(FILE *out);
 #define _PyList_CAST(op) (assert(PyList_Check(op)), (PyListObject *)(op))
 
 #define PyList_GET_ITEM(op, i) (_PyList_CAST(op)->ob_item[i])
-#define PyList_SET_ITEM(op, i, v) (_PyList_CAST(op)->ob_item[i] = (v))
+#define PyList_SET_ITEM(op, i, v) ((void)(_PyList_CAST(op)->ob_item[i] = (v)))
 #define PyList_GET_SIZE(op)    Py_SIZE(_PyList_CAST(op))

Include/cpython/tupleobject.h

@@ -23,6 +23,6 @@ PyAPI_FUNC(void) _PyTuple_MaybeUntrack(PyObject *);
 #define PyTuple_GET_ITEM(op, i) (_PyTuple_CAST(op)->ob_item[i])
 
 /* Macro, *only* to be used to fill in brand new tuples */
-#define PyTuple_SET_ITEM(op, i, v) (_PyTuple_CAST(op)->ob_item[i] = v)
+#define PyTuple_SET_ITEM(op, i, v) ((void)(_PyTuple_CAST(op)->ob_item[i] = v))
 
 PyAPI_FUNC(void) _PyTuple_DebugMallocStats(FILE *out);

Misc/NEWS.d/next/C API/2020-05-06-23-54-57.bpo-30459.N9_Jai.rst

@@ -0,0 +1,2 @@
+Cast the result of :c:func:`PyList_SET_ITEM` and :c:func:`PyTuple_SET_ITEM`
+to void.